Position/time synchronization of unmanned air vehicles for air refueling operations

ABSTRACT

A system and methods for coordinating positioning of vehicles in motion is disclosed. The method graphically presents displayed synchronization parameters on a display screen such that a user determines a planned position of a first vehicle on a planned path in order to arrive at a predetermined position at a correct time. The method further synchronizes the first vehicle with the planned position on the planned path using the displayed synchronization parameters and performs a rendezvous between the first vehicle and a second vehicle.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. 120 from and is acontinuation application of U.S. patent application Ser. No. 12/945,856,filed 13 Nov. 2010, content of which is incorporated herein by referencein its entirety.

FIELD

Embodiments of the present disclosure relate generally to aerialrefueling. More particularly, embodiments of the present disclosurerelate to aircraft synchronization and rendezvous during aerialrefueling.

BACKGROUND

Aerial refueling is a process of transferring fuel from a tankeraircraft to a receiver aircraft during flight. Aerial refueling allowsthe receiver aircraft to extend its range or remain airborne longer. Byaerial refueling after take-off, the receiver aircraft can allow atake-off with a greater payload, since a maximum take-off weight can bemet by carrying less fuel. Probe and drogue, and flying boom are twomain refueling systems. Aerial refueling is a well-established means inaviation to extend the range and duration/loiter of airborne aircraft.With the advent of unmanned aerial vehicles (UAV) and the absence ofhuman pilots, autonomous aerial refueling poses new challenges.

SUMMARY

A method of position/time synchronization of unmanned air vehicles forair refueling operations is disclosed. A current position of a refuelingaircraft is calculated, and a planned position of the refueling aircraftis calculated. Synchronization parameters are graphically displayed suchthat a user determines the planned position of the refueling aircraft ona planned flight path in order to arrive at a predetermined position ata correct time. A calculated bank angle is calculated such that therefueling aircraft intercepts the planned flight path when turned withthe bank angle. The refueling aircraft can turn early at the calculatedbank angle from the current position to reach a future point ahead ofthe planned position on the planned flight path. The refueling aircraftcan then intercept the planned position, and rendezvous with a receiveraircraft. In this manner, a pilot/user can see in real-time his/hercurrent position and plan ahead where to accurately position the tankeraircraft without guesswork. Thereby saving time during refuelingoperation.

In a first embodiment, an aircraft position synchronization systemcomprises a rabbit calculation module operable to calculate a plannedposition of a first aircraft. The system further comprises a displayscreen operable to graphically display synchronization parametersthereon such that a user determines the planned position on a plannedflight path of the first aircraft in order to arrive at a predeterminedposition at a correct time. The system also comprises a rendezvousmodule operable to coordinate the first aircraft with at least onesecond aircraft.

In a second embodiment, a method for synchronizing aircraft positions inflight calculates a planned position of a first aircraft. The methodthen graphically displays synchronization parameters on a display screensuch that a user determines the planned position of the first aircrafton a planned flight path in order to arrive at a predetermined positionat a correct time.

In a third embodiment, a method of coordinating positioning of vehiclesin motion graphically presents displayed synchronization parameters on adisplay screen such that a user determines a planned position of a firstvehicle on a planned path in order to arrive at a predetermined positionat a correct time. The method further synchronizes the first vehiclewith the planned position on the planned path using the displayedsynchronization parameters, and performs rendezvous between the firstvehicle and a second vehicle.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

BRIEF DESCRIPTION OF DRAWINGS

A more complete understanding of embodiments of the present disclosuremay be derived by referring to the detailed description and claims whenconsidered in conjunction with the following figures, wherein likereference numbers refer to similar elements throughout the figures. Thefigures are provided to facilitate understanding of the disclosurewithout limiting the breadth, scope, scale, or applicability of thedisclosure. The drawings are not necessarily made to scale.

FIG. 1 is an illustration of orbit patterns for aerial refuelingoperation showing an orbit pattern of a receiver aircraft in a vicinityof an orbit pattern of a tanker aircraft.

FIG. 2 is an illustration of an enroute refueling rendezvous for areceiver aircraft and a tanker aircraft.

FIG. 3 is an illustration of an orbit pattern of a tanker aircraftshowing position time projection (PTP) according to an embodiment of thedisclosure.

FIG. 4 is an illustration of an effect of winds on a velocity vector ofan aircraft during a banked turn.

FIG. 5 is an illustration of an exemplary aerial refueling operationshowing a tanker aircraft out of a planned position according to anembodiment of the disclosure.

FIG. 6 is an illustration of the exemplary orbit pattern of the tankeraircraft of FIG. 5 showing that the tanker aircraft is performing afirst banked turn in order to select an intercept point for the plannedposition on its orbit pattern according to an embodiment of thedisclosure.

FIG. 7 is an illustration of the exemplary orbit pattern of the tankeraircraft of FIG. 6 showing the tanker aircraft of FIG. 6 is now about2.5 minutes late according to an embodiment of the disclosure.

FIG. 8 is an illustration of the orbit pattern of the tanker aircraft ofthe FIG. 7 showing the tanker aircraft has increased its bank angle in asecond banked turn to intercept the planned position (rabbit) on timeaccording to an embodiment of the disclosure.

FIG. 9 is an illustration of the orbit pattern of the tanker aircraft ofthe FIG. 8 showing the tanker aircraft is now in sync with the plannedposition according to an embodiment of the disclosure.

FIG. 10 is an illustration of an exemplary orbit pattern of a tankeraircraft showing effect of bank angle of the tanker aircraft onposition-time projection and immediate feedback to a pilot according toan embodiment of the disclosure.

FIG. 11 is an illustration of an exemplary air refueling synchronizationshowing an orbit pattern of a tanker aircraft and orbit patterns of tworeceiver aircraft according to an embodiment of the disclosure.

FIG. 12 is an illustration of an exemplary air refueling rendezvousafter missed attempt according to an embodiment of the disclosure.

FIG. 13 is an illustration of an exemplary radio communication system ofa tanker aircraft and a receiver aircraft according to an embodiment ofthe disclosure.

FIG. 14 is an illustration of an exemplary functional block diagram ofair refueling synchronization and rendezvous system according to anembodiment of the disclosure.

FIG. 15 is an illustration of an exemplary flowchart showing an airrefueling synchronization and rendezvous process according to anembodiment of the disclosure.

FIG. 16 is an illustration of an exemplary flowchart showing a processfor coordinating positions of vehicles in motion according to anembodiment of the disclosure.

DETAILED DESCRIPTION

The following detailed description is exemplary in nature and is notintended to limit the disclosure or the application and uses of theembodiments of the disclosure. Descriptions of specific devices,techniques, and applications are provided only as examples.Modifications to the examples described herein will be readily apparentto those of ordinary skill in the art, and the general principlesdefined herein may be applied to other examples and applications withoutdeparting from the spirit and scope of the disclosure. Furthermore,there is no intention to be bound by any expressed or implied theorypresented in the preceding technical field, background, brief summary orthe following detailed description. The present disclosure should beaccorded scope consistent with the claims, and not limited to theexamples described and shown herein.

Embodiments of the disclosure may be described herein in terms offunctional and/or logical block components and various processing steps.It should be appreciated that such block components may be realized byany number of hardware, software, and/or firmware components configuredto perform the specified functions. For the sake of brevity,conventional techniques and components related to aircraft refuelingsystems, flight control systems, equations of motion, displaytechnology, aircraft operation, and other functional aspects of thesystems (and the individual operating components of the systems) may notbe described in detail herein. In addition, those skilled in the artwill appreciate that embodiments of the present disclosure may bepracticed in conjunction with a variety of different aircraft controlsystems, electrical systems and aircraft wing configurations, and thatthe system described herein is merely one example embodiment of thedisclosure.

Embodiments of the disclosure are described herein in the context ofpractical non-limiting applications, namely, aerial refueling.Embodiments of the disclosure, however, are not limited to such aerialrefueling, and the techniques described herein may also be utilized inother refueling applications. For example, embodiments may be applicableto ship refueling, helicopter-ship refueling, fuel tanker-vehicle groundrefueling, and the like.

As would be apparent to one of ordinary skill in the art after readingthis description, the following are examples and embodiments of thedisclosure, and are not limited to operating in accordance with theseexamples. Other embodiments may be utilized and structural changes maybe made without departing from the scope of the exemplary embodiments ofthe present disclosure.

Aerial refueling is a process of transferring fuel from a tankeraircraft to a receiver aircraft during flight. The tanker aircraft maycomprise, for example but without limitation, narrow body jetliners,wide body jetliners, helicopters, and the like. The receiver aircraftmay comprise, for example but without limitation, jet fighters, cargoplanes, passenger aircraft, narrow body jetliners, wide body jetliners,helicopters, and the like.

Aerial refueling is a well-established means in aviation to extend therange and duration/loiter of airborne aircraft. With the advent ofunmanned aerial vehicles (UAV) and the absence of human pilots,autonomous aerial refueling poses new challenges. Embodiments of thedisclosure provide a reliable solution to autonomous tanker and UAVrendezvous is that significantly increase the mission capabilities ofUAVs. The embodiments provide means to coordinate a tanker aircraft andat least one receiving aircraft of any type to arrive at a common eventpoint in spatial coordinates at a specific time such that refuelingoperations can commence.

FIG. 1 is an illustration of existing orbit patterns 100 for aerialrefueling operation showing a receiver aircraft orbit pattern 102(receiver orbit pattern 102) of a receiver aircraft 104 in a vicinity ofa tanker aircraft orbit pattern 106 (tanker orbit pattern 106) of atanker aircraft 108. In the example embodiment shown in FIG. 1, thetanker orbit pattern 106 for point parallel/anchor rendezvous proceduresis a racetrack pattern to the left, using 2 minute legs 110 and 30degree banked turns with an Air Refueling Control Point (ARCP) 112. TheARCP 112 is the primary reference for the rendezvous. The ARCP 112 is aplanned geographical point over which the receiver aircraft 104 arrivesin an observation/pre-contact position with respect to the tankeraircraft 108, at a downstream end of the 2 minute leg 110 that coincideswith an inbound rendezvous track 114 of the receiver aircraft 104. Thereceiver aircraft 104 calls in to the tanker aircraft 108 at an AirRefueling Initial Point (ARIP) 116. The ARIP 116 is a point (rendezvousposition) upstream from the ARCP 112 at which the receiver aircraft 104initiates a rendezvous with the tanker aircraft 108. The ARIP 116 is a15 minute call point (15 minutes prior to the Air Refueling Control Time(ARCT). An ARCT is the receiver aircraft planned arrival time at anARCP. At the ARIP 116, the receiver aircraft 104 transmits information,such as but without limitation, call sign, estimated time of arrival(ETA) (on time, minutes early, or minutes late), altitude, and the like,to the tanker aircraft 108. Similarly, at the ARIP 116 the tankeraircraft 108 transmits information, such as but without limitation, airrefueling altitude, altitude, timing (on time, minutes early, or minuteslate), and the like, to the receiver aircraft 104.

The ARIP 116 is reached when the receiver aircraft 104 is on the inboundrendezvous track 114. The tanker aircraft 108 altitude, ARCP, ARIP andthe ARCT are given in the mission plan/air tasking technical orders.Airspeed of the tanker aircraft 108 and the receiver aircraft 104 arealso set according to an air refueling technical order for each receiveraircraft. The range 122 to begin turn at a point 118 to rendezvous iscalculated by the user/pilot or copilot. A turn is executed when theonboard ranging equipment (Terrain Collision Avoidance System (TCAS))states the range 122 is equal to the calculated range. The receiveraircraft 104 maintains about 1000 feet below air refueling base altitudeuntil visual contact is established (e.g., visual contact must be madeat 1 nm or in accordance with technical order visibility for rendezvousclosure) with the tanker aircraft 108. The range 122 at which to turn iscalculated by knowing an offset and velocity of the receiver aircraft104 and the tanker aircraft 108, and is determined such that the tankeraircraft 108 is about 1-3 nmi in front of the receiver aircraft 104 whenthe tanker aircraft 108 completes its turn. The offset is a calculateddisplaced lateral distance (i.e., a minor diameter of the orbit pattern106) between the tanker aircraft 108 at the 2 minute leg 110 and an airfueling track 120 that allows the tanker aircraft 108 to turn in frontof the receiver 1-3 miles on the air refueling track 120 inbound to theARCP 112. From the offset, a bank angle θ (or vice versa) can bedetermined by the following equation:

$\begin{matrix}{{r\left( {\frac{1}{2}{offset}} \right)} = \frac{v^{2}}{11.26\mspace{14mu}\tan\;(\theta)}} & (1)\end{matrix}$

Where θ is the bank angle, r is radius of the turn, and ν is theaircraft velocity in knots.

Then the receiver aircraft 104 makes a controlled closure on the tankeraircraft 108 and refueling operations begin along the air fueling track120. In an event the receiver aircraft 104 arrive early, the receiverorbits at the ARIP 116.

FIG. 2 is an illustration of an existing enroute refueling rendezvous200 for the receiver aircraft 104 and the tanker aircraft 108. Forenroute procedures, the rendezvous comprises both aircraft flying to theARIP 116 within one minute of each other and then along a common track120 to the ARCP 112. Tanker aircraft 108 (or multiple tanker aircraft)and receiver aircraft 104 (or multiple receiver aircraft) may join up ata rendezvous point (RZ) by controlling the timing so they arrive at theRZ at the same time. Timing to the RZ may be adjusted using differentialairspeeds, orbit delays or timing triangles.

Embodiments of the disclosure calculate and indicate on a display screenwhere the tanker aircraft 108 and receiver aircraft 104 need to be atany given time in order to initiate aerial refueling.

According to embodiments of the disclosure at least two position-timeprojections are displayed on a display screen as explained in moredetail below. One is a planned position and one is a real-timeprojection based on a current position, velocity, attitude, and windfrom the Inertial Navigation System (INS) and/or the Global PositioningSystem (GPS). The planned position (or rabbit) represents where thetanker aircraft 108 must be in order to begin refueling operations givena known position of the receiver aircraft 104. The pilot/user can see inreal-time his/her current position and plan ahead where to position thetanker aircraft 108 without mental calculation and guesswork.

FIG. 3 is an illustration of a tanker orbit pattern 302 of a tankeraircraft 304 showing position-time projection (PTP) according to anembodiment of the disclosure. The PTP is a display of planned positionvs. time. The PTP illustrates where the tanker aircraft 304 must be atany given time on the tanker orbit pattern 302. The planned position 306at a current/actual time is called a rabbit (rabbit/rabbit position306). From the rabbit 306, a set of dashed lines are marked on a plannedposition-time projection vector 314 (planned flight path 314) to showplanned future positions, for example, in 30 sec increments ahead of therabbit 306. A waypoint on the planned flight path 314 is selected as thesynchronization point (usually the ARCP 112) and pilot/user sets thetime he/she wants to arrive at that point. The waypoint may also beselected locally via an autopilot, or remotely via a user. As a realtime clock runs the rabbit 306 and its planned velocity vector 312 movealong the planned flight path 314 showing the pilot/user where on theplanned flight path 314 the tanker aircraft 304 needs to be positionedin order to arrive at the ARCP 112 at the correct time. The current oractual position-time flight path projection vector 310 (actual flightpath 310) is the same position-time flight path projection vector usedin modern aircraft. The planned flight path 310 is projected using thecurrent aircraft attitude, position, ground speed and headingtransmitted from the attitude reference system. The actual flight path310 is displayed in 30 second increments similar to the planned flightpath 314. If wind data is available, the position-time projection vector310 can reflect the effects of the winds on the planned velocity vector312 of the planned flight 314 as shown in FIG. 4.

FIG. 4 is an illustration of effect of winds on a velocity vector of thetanker aircraft 304 during a banked turn 410 according to an embodimentof the disclosure. A tail wind 402 relative to the ground extends theplanned velocity vector 312, and a head wind 404 retards the plannedvelocity vector 312 relative to the ground. In this manner, in a 180degree banked turn 410 the planned velocity vector 312 comprises acombination of effect of both the tail wind 402 and the head wind 404resulting in planned velocity vectors 406 and 408 respectively.

FIGS. 5-9 illustrate an aerial refueling scenario according anembodiment of the disclosure.

FIG. 5 is an illustration of an exemplary aerial refueling operationshowing a tanker aircraft 502 out of position according to an embodimentof the disclosure.

FIG. 6 is an illustration of an exemplary orbit pattern 510 of a tankeraircraft 502 showing the tanker aircraft 502 is banked in banked turn604 in order to select an intercept point for a planned position 504(rabbit/rabbit position 504) on the orbit pattern 510 according to anembodiment of the disclosure.

FIG. 7 is an illustration of an exemplary orbit pattern 510 of a tankeraircraft 502 showing the tanker aircraft 510 of the FIG. 6 is now about2.5 minutes late according to an embodiment of the disclosure.

FIG. 8 is an illustration of the orbit pattern 510 of the tankeraircraft 502 of the FIG. 7 showing the tanker aircraft 502 has increasedits bank angle θ in a second turn to intercept the planned position 504(rabbit position 504) on time according to an embodiment of thedisclosure.

FIG. 9 is an illustration of the orbit pattern 510 of the tankeraircraft 502 of the FIG. 8 showing the tanker aircraft 502 is now insync with the planned flight path 514 according to an embodiment of thedisclosure.

FIG. 5 shows the tanker aircraft 502 planned position-time projectionvector 514 (planned flight path 514), a planned position 504(rabbit/rabbit position 504), an actual/current position 506, and theactual position-time projection vector 310 (actual flight path 310).This scenario can come about by a change in the ARCP 112 duringrefueling operations, for instance when an unplanned receiver approachesfrom the opposite direction of the current refueling mission plan. Inthis hypothetical case the ARCP 112 is changed to accommodate the newreceiver. To synchronize the tanker aircraft 502 in this scenario, thepilot will begin to execute a left banked turn 604 several minutesbefore it is a beam of the planned position 504 as shown in FIG. 6. Inthe existing solution the pilot has no reliable way to assess whetherhis/her bank angle θ (i.e., turn rate {dot over (θ)}) is too much or toolittle. The result is poor synchronization with the planned flight path514. In contrast, according to embodiments of the disclosure, the pilotcan correctly assess what bank angle θ will correctly synchronizehis/her plane with the planned flight path 514. FIG. 6 shows the pilotmaking the banked turn 604 towards the rabbit position 504. Since thetanker aircraft 502 is positioned on the opposite side of the tankerorbit 510, it may take more than one banked turn 604 to synch with therabbit position 504 because by the time the tanker aircraft 502 executesits 4 minute banked turn, the rabbit position 504 has also progressed 4minutes down the planned flight path 514. The tanker aircraft 502 can“catch the rabbit” at the next turn, as shown in FIG. 7. The tankeraircraft 502 arrives on the planned flight path 514 about 2.5 minuteslate and “catches up” in the next turn. FIG. 8 shows the pilot slowlyincreasing the bank angle θ until the planned flight path 514 and theactual flight path 802 meet at a selected time (3.5 minutes in thisexample). In this manner, the actual flight path 802 intercepts therabbit position 504 at position 804 after it makes the planned turn. Thetanker aircraft 502 is now synched with the planned flight path 514 asshown in FIG. 9. FIG. 10 shows an effect of bank angle θ on theposition-time-projection and an immediate feedback the pilot sees on thedisplay screen 1404 (FIG. 14).

FIG. 10 is an illustration of an exemplary tanker orbit pattern 1002 ofa tanker aircraft 1004 showing the effect of bank angle θ of the tankeraircraft 1004 on actual position-time projection vectors 11010/1008/1012(actual flight path 1010/1008/1012) and substantially immediate feedbackthat can be observed on the display screen 1404 (FIG. 14) by apilot/user according to an embodiment of the disclosure. FIG. 10 showsan effect of a correct amount of bank angle θ on the actual flight path1008, too much bank angle θ on the actual flight path 1010, and toolittle bank angle θ on the actual flight path 1012. As explained in moredetail below, system 1400 determines for the pilot/user when to turn andhow much bank angle θ is required to intercept the planned flight path514 on the rabbit position 504.

FIG. 11 is an illustration of an exemplary aerial refuelingsynchronization showing a tanker orbit pattern 1102 of a tanker aircraft1104 and orbit patterns 1110 and 1112 of two receiver aircraft 1106 and1108 respectively according to an embodiment of the disclosure. Thereceiver aircraft 1106/1108 and the tanker aircraft 1104 may be, forexample but without limitation, a UAV, a manned aircraft, or the like.In this example, UAVs are used for the receiver aircraft 1106/1108 andthe tanker aircraft 1104. Facilitating rendezvous between the receiveraircraft 1106/1108 (UAV 1106/1108) and the tanker aircraft 1104 can beaccomplished by using the position-time projection method describedabove. A UAV 1106/1108 mission comprises a refueling operation. The UAV1106/1108 communicates with the tanker aircraft 1104 to let the tankeraircraft 1104 know the UAV 1106/1108 type and initial position ARIP11114/ARIP2 1120, which ensures a timing of the air refueling operationis coordinated. As shown in FIG. 11 the receiver aircraft 1106/1108 issynced to the tanker aircraft 1104 position and speed using a plannedposition-time projection vector 1122/1124 (UAV planned flight path1122/1124) on the receiver aircraft orbit pattern 1110/1112. The UAV1106/1108 continues to fly the receiver aircraft orbit pattern 1110/1112tracking the tanker aircraft 1104 planned position-time projectionvector 1126 (planned flight path 1126). When the tanker aircraft 1104arrives at the ARCP1 1116/ARCP2 1120 the UAV 1106/1108 should be in arendezvous position such as the ARIP1 1114/ARIP2 1118 to accomplish therendezvous and begin refueling. After refueling, the UAV 1106/1108 exitsthe orbit patterns 1110/1112 by flying a pre-determined flight path andthen continues on with its mission (flies to the first post-fuelingwaypoint in a mission plan), and the tanker aircraft 1104 initiates arendezvous sequence with the next receiver aircraft 1106/1108. Thebenefit is safe, efficient UAV refueling operations allowing severalaircraft to be refueled in a given amount of time. In the event thereceiver aircraft 1106/1108 misses the tanker rendezvous, another orbitpattern can be initiated as shown in FIG. 12. The system 1400 explainedbelow computes the most efficient rendezvous flight paths for eachaircraft and guide them to the ARCP1 1116/ARCP2 1120 at the newdesignated Air Refueling Control Time (ARCT). When refueling a mannedvehicle, standard procedure is for the tanker aircraft 1104 to completeits rendezvous turn 3 nmi in front of the receiver aircraft 1106/1108,allowing the receiver aircraft 1106/1108 to make a controlled closure onthe tanker aircraft 1104. The same protocol exists in the UAV scenario.The UAV 1106/1108 comprises communications onboard first to alert thetanker aircraft 1104 that the UAV 1106/1108 is ready to begin refuelingrendezvous operations (i.e., it is in its orbit pattern 1110/1112), andsecond to receive the commands such as waypoints and associated desiredvelocities, from the tanker aircraft 1104.

FIG. 12 is an illustration of an exemplary air refueling rendezvousafter missed attempt according to an embodiment of the disclosure. Ifthe receiver aircraft 1106/1108 misses the sync, the tanker aircraft1104 performs a bank turn 1206 and comes around. In this manner, thetanker aircraft 1104 communicates with the receiver aircraft 1106/1108to determine the receiver aircraft 1106/1108 position and to determineits required bank angle θ thereupon.

FIG. 13 is an illustration of an exemplary radio communication system(system 1300) for communication between the tanker aircraft 1104 and thereceiver aircraft 1106 according to an embodiment of the disclosure. Apractical embodiment of the system 1300 comprises additional componentsand elements configured to support known or conventional operatingfeatures that need not be described in detail herein. The system 1300generally comprises a tanker aircraft transceiver module 1302, areceiver aircraft transceiver module 1304, a tanker aircraft GPS module1310, a receiver aircraft receiver GPS module 1312, a tanker aircraftsynchronization and rendezvous module 1314, and a receiver aircraftsynchronization and rendezvous module 1314.

In the example embodiment, the system 1300 can be used to transmit andreceive aircraft performance parameters from the receiver aircraft1106/1108 to and from the tanker aircraft 1104. A query from the tankeraircraft transceiver module 1302 may be sent to the receiver aircrafttransceiver module 1304 seeking position and velocity of same inanticipation to a sync event. In this manner, the receiver aircrafttransceiver module 1304 transmits position and velocity information ofthe receiver aircraft 1106/1108 aircraft to the tanker aircrafttransceiver module 1302. The tanker aircraft transceiver module 1302continuously and automatically receives the performanceinformation/parameters of the receiver aircraft 1106/1108 for a durationof the sync event and automatically adjusts its bank angle if necessarybased on the performance information until synched.

The system 1300 may comprise any number of communication modules, anynumber of network communication modules, any number of processormodules, and any number of memory modules. The system 1300 illustratedherein depicts a simple embodiment for ease of description. A practicalembodiment of the wireless radio communication environment 1300comprises additional components and elements configured to support knownor conventional operating features. For the sake of brevity,conventional techniques and components related to digital signalprocessing such as channel encoding/decoding, correlation techniques,spreading/dispreading, pulse shaping, radio frequency (RF) technology,and other functional aspects and the individual operating components ofthe wireless radio communication environment 1300 may not be describedin detail herein.

In the example system 1300, the receiver aircraft transceiver module1304 and the tanker aircraft transceiver module 1302 each comprise atransmitter module and a receiver module (not shown in FIG. 13). Thereceiver aircraft transceiver module 1316 and the tanker aircrafttransceiver module 1302 are configured to communicate via a wirelessdata communication link 1320.

For this example, the tanker aircraft transceiver module 1314, and thereceiver aircraft transceiver module 1316 are each coupled to theirrespective RF antenna arrangement 1306 and 1308 that can support aparticular wireless communication protocol and modulation scheme toreceive and transmit position and performance parameters respectively.The tanker aircraft transceiver module 1302 and the receiver aircrafttransceiver module 1304 are each coupled to the tanker aircraft GPSmodule 1310 and the receiver aircraft GPS module 1312 respectively. Inthis manner, a current position of the tanker aircraft 1104 and acurrent position of the receiver aircraft 1106/1108 are determined andcommunicated therebetween using the transceiver modules 1302/1304. Theperformance parameters may comprise, for example but without limitation,aircraft velocity, aircraft coordinates, the receiver aircraft 1106/1108indication of contact with the tanker aircraft 1104, an aircraft actualposition, the receiver aircraft 1106/1108 waypoints, the receiveraircraft 1106/1108 waypoints desired velocities, and the like.

The tanker aircraft synchronization and rendezvous module 1314, andreceiver aircraft synchronization and rendezvous module 1316 are eachconfigured to synchronize the tanker aircraft 1104 to the rabbit 504 onthe orbit thereof and allow the receiver aircraft 1106/1108 and thetanker aircraft 1104 to meet at a predetermined position such as theARCP1 1116/ARCP2 1120. The tanker aircraft synchronization andrendezvous module 1314, and the receiver aircraft synchronization andrendezvous module 1316 are explained in more detail below.

FIG. 14 is an illustration of an exemplary functional block diagram ofaerial refueling synchronization and rendezvous system 1400 (1314/1316in FIG. 13) according to an embodiment of the disclosure. The system1400 may comprise a display module 1402, a rabbit calculation modulation1406, a bank angle calculation module 1408, a rendezvous module 1410, aprocessor module 1412, a memory module 1414, and a communication module1416. These and other elements of the system 1400 may be interconnectedtogether using a data communication bus 1418 or any suitablewired/wireless interconnection arrangement. Such interconnectionfacilitates communication between the various elements of the system1400.

System 1400 may be part of a network architecture that communicates withthe receiver aircraft 1106/1108, or be a standalone portable device suchas a mobile phone, a personal digital assistant (PDA) such as aBlackberry™ device, Palm Treo, iPod™, iPad™, or other similar portabledevice. In some embodiments the system 1400 may be, for example butwithout limitation, a personal wireless computer such as a wirelessnotebook computer, a wireless palmtop computer, or other mobile computerdevice.

The display module 1402 may comprise, for example but withoutlimitation, a Horizontal Situation Indicator (HSI), a display screen ona flight deck computer, a display module on a ground control computer, adisplay module on portable computer, and the like. The display module1402 comprises a display screen 1404 to provide a visual aid for theuser/pilot. For example, as a real time clock runs, the rabbit position504 (FIG. 5) and its velocity vector 512 move along the planned flightpath 314 graphically displaying for the pilot where on the plannedflight path 514 the tanker aircraft 506 needs to be positioned in orderto arrive at a predetermined position such as the ARCP 112 at thecorrect time. In this manner, the display screen 1404 of the displaymodule 1402 graphically displays synchronization parameters insubstantially real-time. The synchronization parameters may comprise,for example but without limitation, a calculated turn/bank angle, theplanned position (rabbit) 504 on the planned flight path 514, theplanned flight path 514, the actual position 506, the actual flight path310 (current flight path 310), the orbit pattern 510, and the like. Thedisplay screen 1404 of display module 1402 may comprise an image displaydevice such as but without limitation, a light emitting diode (LED)display, a liquid crystal display (LCD), or an organic EL display(OLED). The display module 1402 may be used to display an imagecorresponding to images provided by the processor module 1412.

The rabbit calculation modulation 1406 calculates the planned position(rabbit position) 504 of the tanker aircraft 502/1104 and/or thereceiver aircraft 1106/1108. The tanker aircraft 502/1104 and/or thereceiver aircraft 1106/1108 may be referred to as aircraft herein. Therabbit position 504 and the planned flight path 514 are calculated usinga predetermined set of flight performance parameters such as aircrafttranslational and rotational speeds, for each aircraft and a set ofwaypoints that define the orbit pattern 510. A time is designated (e.g.,Greenwich Mean Time (GMT)) for the tanker aircraft 1104 to arrive at theARCP 112. A calculation process then starts from the ARCP 112 positionat the designated arrival time and flies backward along the orbitpattern 510 using the selected flight performance parameters to thecurrent time and places the rabbit position 504 at that location.

The bank angle calculation module 1408 determines for the pilot/userwhen to turn and how much bank angle θ is required to intercept theplanned flight path 514 on the rabbit position 504. In this manner, thepilot can correctly assess what bank angle θ will correctly synchronizehis/her aircraft with the planned flight path 514. The bank angle θ maybe calculated based on the following relationship:

$\begin{matrix}{{r = \frac{v^{2}}{g\mspace{20mu}{\tan(\theta)}}},} & (2)\end{matrix}$

where θ is the bank angle, r is radius of the turn, g is gravitationalacceleration, and ν is the aircraft velocity. Equation 2 is based onforces acting on the aircraft in a steady state turn at a constant bankangle θ. The aircraft turns due to the horizontal component of lift.Centripetal force

$\frac{v^{2}}{r}$which is a horizontal component of lift in a turn can be solved usingequation 2. In this manner, the radius of the turn r and the bank angleθ can be derived by knowing the aircraft velocity ν, the gravitationalacceleration g, and one of the radius of the turn r and the bank angleθ.

The rendezvous module 1410 computes a substantially most efficientrendezvous flight path for each receiver aircraft 1106/1108 and guideeach receiver aircraft 1106/1108 to the ARCP1 1116/ARCP2 1120 at the newdesignated Air Refueling Control Time (ARCT) as explained above.

The processor module 1412 comprises processing logic that is configuredto carry out the functions, techniques, and processing tasks associatedwith the operation of the system 1400. In particular, the processinglogic is configured to support the synchronization and rendezvousfunction of the system 1400 described herein. For example, the processormodule 1412 may be suitably configured to receive the performance andposition information of the receiver aircraft 1106/1108 and tankeraircraft 1104 from the transceiver modules 1304 and 1302.

The processor module 1412 may be implemented, or realized, with ageneral purpose processor, a content addressable memory, a digitalsignal processor, an application specific integrated circuit, a fieldprogrammable gate array, any suitable programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof, designed to perform the functions described herein.In this manner, a processor may be realized as a microprocessor, acontroller, a microcontroller, a state machine, or the like. A processormay also be implemented as a combination of computing devices, e.g., acombination of a digital signal processor and a microprocessor, aplurality of microprocessors, one or more microprocessors in conjunctionwith a digital signal processor core, or any other such configuration.

Furthermore, the steps of a method or algorithm described in connectionwith the embodiments disclosed herein may be embodied directly inhardware, in firmware, in a software module executed by processor module1412, or in any practical combination thereof. A software module mayreside in the memory module 1414, which may be realized as RAM memory,flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a harddisk, a removable disk, a CD-ROM, or any other form of storage mediumknown in the art. In this regard, the memory module 1414 may be coupledto the processor module 1412 such that the processor module 1412 canread information from, and write information to, memory module 1414. Forexample, processor module 1412 and the memory module 1414 may be inrespective ASICs. The memory module 1414 may also be integrated into theprocessor module 1412. In an embodiment, the memory module 1414 mayinclude a cache memory for storing temporary variables or otherintermediate information during execution of instructions to be executedby processor module 1412. The memory module 1414 may also includenon-volatile memory for storing instructions to be executed by theprocessor module 1412.

The communication module 1416 transmits and receives data from and tothe tanker aircraft transceiver module 1302, the receiver aircrafttransceiver module 1304, the tanker aircraft GPS module 1310, and thereceiver aircraft receiver GPS module 1306. In this example, thecommunication module 1416 comprises a transmitter module and a receivermodule (not shown in FIG. 14). The communication module 1416, is coupledto an RF antenna arrangement (not shown) that can support a particularwireless communication protocol and modulation scheme to, for examplebut without limitation, receive position and performance parameters ofthe tanker aircraft 1104 and the receiver aircraft 1106/1108, andtransmit, for example but without limitation, the rabbit position 1008,the calculated bank angle θ, and the like.

FIG. 15 is an illustration of an exemplary flowchart showing an airrefueling synchronization and rendezvous process 1500 according to anembodiment of the disclosure. The various tasks performed in connectionwith process 1500 may be performed, by software, hardware, firmware, acomputer-readable medium having computer executable instructions forperforming the process method, or any combination thereof. The process1500 may be recorded in a computer-readable medium such as asemiconductor memory, a magnetic disk, an optical disk, and the like,and can be accessed and executed, for example, by a computer CPU such asthe processor module 1412 in which the computer-readable medium isstored. It should be appreciated that process 1500 may include anynumber of additional or alternative tasks, the tasks shown in FIG. 15need not be performed in the illustrated order, and process 1500 may beincorporated into a more comprehensive procedure or process havingadditional functionality not described in detail herein. Forillustrative purposes, the following description of process 1500 mayrefer to elements mentioned above in connection with FIGS. 3-14. Inpractical embodiments, portions of the process 1500 may be performed bydifferent elements of the system 1300 and system 1400 such as: the atanker aircraft transceiver module 1302, the receiver aircrafttransceiver module 1304, the tanker aircraft GPS module 1310, thereceiver aircraft receiver GPS module 1312, the display module 1402, therabbit calculation modulation 1406, the bank angle calculation module1408, the rendezvous module 1410, the processor module 1412, the memorymodule 1414, and the communication module 1416. Process 1500 may havefunctions, material, and structures that are similar to the embodimentsshown in FIGS. 3-14. Therefore common features, functions, and elementsmay not be redundantly described here.

Process 1500 may begin by calculating the planned position 504 of thefirst aircraft such as the tanker aircraft 502 (task 1502).

Process 1500 may continue by displaying synchronization parametersgraphically such that a user determines the planned position 504 of thefirst aircraft on a planned flight path 514 in order to arrive at apredetermined position such as the ARCP 112 at a correct time (task1504).

Process 1500 may continue by calculating a calculated bank angle θ suchthat the first aircraft intercepts the planned flight path 514 whenturned with the calculated bank angle θ (task 1506).

Process 1500 may continue by turning early at the calculated bank anglefrom the current position 506 to reach a future point 804 ahead of theplanned position 504 on the planned flight path 514 (task 1508).

Process 1500 may continue by intercepting the planned position 504 (task1510).

FIG. 16 is an illustration of an exemplary flowchart showing process1600 for coordinating vehicles in motion according to an embodiment ofthe disclosure. The various tasks performed in connection with process1600 may be performed, by software, hardware, firmware, acomputer-readable medium having computer executable instructions forperforming the process method, or any combination thereof. The process1600 may be recorded in a computer-readable medium such as asemiconductor memory, a magnetic disk, an optical disk, and the like,and can be accessed and executed, for example, by a computer CPU such asthe processor module 1412 in which the computer-readable medium isstored. It should be appreciated that process 1600 may include anynumber of additional or alternative tasks, the tasks shown in FIG. 16need not be performed in the illustrated order, and process 1600 may beincorporated into a more comprehensive procedure or process havingadditional functionality not described in detail herein. Forillustrative purposes, the following description of process 1600 mayrefer to elements mentioned above in connection with FIGS. 3-14. Inpractical embodiments, portions of the process 1600 may be performed bydifferent elements of the system 1300 and system 1400 such as: the atanker aircraft transceiver module 1302, the receiver aircrafttransceiver module 1304, the tanker aircraft GPS module 1310, thereceiver aircraft receiver GPS module 1312, the display module 1402, therabbit calculation modulation 1406, the bank angle calculation module1408, the rendezvous module 1410, the processor module 1412, the memorymodule 1414, and the communication module 1416.

Process 1600 may begin by graphically presenting displayedsynchronization parameters on a display screen 1404 such that a userdetermines a planned position of a first vehicle on a planned path inorder to arrive at a predetermined at a correct time (task 1602).

Process 1600 may than continue by synchronizing the first vehicle withthe planned position on the planned path using the displayedsynchronization parameters (task 1604). In this manner, a GPS modulesuch as the tanker aircraft GPS module 1310 calculates a currentposition of the first vehicle (task 1606), the rabbit calculation module1406 calculates the planned position of the first vehicle (task 1608),the bank angle calculation module 1408 calculates a turn angle such thatthe first vehicle intercepts the planned path when turned with the turnangle (task 1610). The displayed synchronization parameters maycomprise, for example but without limitation, a calculated turn angle, aplanned position on a planned path, a planned path, an orbit pattern, acurrent path, and the like.

Process 1600 may then continue by the first vehicle turning at thecalculated turn angle from the current position to reach a future pointahead of the planned position on the planned path (task 1612).

Process 1600 may then continue by intercepting the planned position(task 1614).

Process 1600 may then continue by performing rendezvous between thefirst vehicle and a second vehicle (task 1616). In this manner, thesystem 1300 communicates the performance parameters between the firstvehicle and the second vehicle, and the bank angle calculation module1408 determines the turn angle for the first vehicle for turning aheadof the planned position to allow rendezvous with the second vehicle. Theperformance parameters comprise, for example but without limitation, afirst vehicle velocity, a first vehicle coordinates, a second vehiclecoordinates, a second vehicle velocity, a second vehicle waypoints, anda second vehicle waypoints desired velocities, timing information suchas estimated time of arrival (ETA) (on time, minutes early, or minuteslate), altitude, and the like.

In this way, embodiments of the disclosure provide systems and methodsthat provide a synchronization and rendezvous for aircraft. Embodimentsautomatically calculate a planned position and indicate same on adisplay screen to show where the aircraft needs to be at any given time.

When implemented in software or firmware, various elements of thesystems 1300-1400 described herein are essentially the code segments orinstructions that perform the various tasks. The program or codesegments can be stored in a processor-readable medium or transmitted bya computer data signal embodied in a carrier wave over a transmissionmedium or communication path. The “processor-readable medium” or“machine-readable medium” may include any medium that can store ortransfer information. Examples of the processor-readable medium includean electronic circuit, a semiconductor memory device, a ROM, a flashmemory, an erasable ROM (EROM), a floppy diskette, a CD-ROM, an opticaldisk, a hard disk, a fiber optic medium, an RF link, or the like.

Those skilled in the art will understand that the various illustrativeblocks, modules, circuits, and processing logic described in connectionwith the embodiments such as system 1300-1400 disclosed herein may beimplemented in hardware, computer-readable software, firmware, or anypractical combination thereof. To clearly illustrate thisinterchangeability and compatibility of hardware, firmware, andsoftware, various illustrative components, blocks, modules, circuits,and steps are described generally in terms of their functionality.Whether such functionality is implemented as hardware, firmware, orsoftware depends upon the particular application and design constraintsimposed on the overall system. Those familiar with the conceptsdescribed herein may implement such functionality in a suitable mannerfor each particular application, but such implementation decisionsshould not be interpreted as causing a departure from the scope of thepresent invention. While at least one example embodiment has beenpresented in the foregoing detailed description, it should beappreciated that a vast number of variations exist. It should also beappreciated that the example embodiment or embodiments described hereinare not intended to limit the scope, applicability, or configuration ofthe subject matter in any way. Rather, the foregoing detaileddescription will provide those skilled in the art with a convenient roadmap for implementing the described embodiment or embodiments. It shouldbe understood that various changes can be made in the function andarrangement of elements without departing from the scope defined by theclaims, which includes known equivalents and foreseeable equivalents atthe time of filing this patent application.

The above description refers to elements or nodes or features being“connected” or “coupled” together. As used herein, unless expresslystated otherwise, “connected” means that one element/node/feature isdirectly joined to (or directly communicates with) anotherelement/node/feature, and not necessarily mechanically. Likewise, unlessexpressly stated otherwise, “coupled” means that oneelement/node/feature is directly or indirectly joined to (or directly orindirectly communicates with) another element/node/feature, and notnecessarily mechanically. Thus, although FIGS. 13-14 depict examplearrangements of elements, additional intervening elements, devices,features, or components may be present in an embodiment of thedisclosure.

Terms and phrases used in this document, and variations thereof, unlessotherwise expressly stated, should be construed as open ended as opposedto limiting. As examples of the foregoing: the term “including” shouldbe read as mean “including, without limitation” or the like; the term“example” is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof; and adjectivessuch as “conventional,” “traditional,” “normal,” “standard,” “known” andterms of similar meaning should not be construed as limiting the itemdescribed to a given time period or to an item available as of a giventime, but instead should be read to encompass conventional, traditional,normal, or standard technologies that may be available or known now orat any time in the future. Likewise, a group of items linked with theconjunction “and” should not be read as requiring that each and everyone of those items be present in the grouping, but rather should be readas “and/or” unless expressly stated otherwise. Similarly, a group ofitems linked with the conjunction “or” should not be read as requiringmutual exclusivity among that group, but rather should also be read as“and/or” unless expressly stated otherwise. Furthermore, although items,elements or components of the disclosure may be described or claimed inthe singular, the plural is contemplated to be within the scope thereofunless limitation to the singular is explicitly stated. The presence ofbroadening words and phrases such as “one or more,” “at least,” “but notlimited to” or other like phrases in some instances shall not be read tomean that the narrower case is intended or required in instances wheresuch broadening phrases may be absent.

The invention claimed is:
 1. An aircraft position synchronization systemcomprising: a processor module connected to a memory module wherein thememory module includes instructions that when executed performs themethod of: calculating a planned position on an orbit pattern of a firstaircraft in flight; and calculating a calculated bank angle based on oneor more performance parameters of at least one second aircraft such thatthe first aircraft intercepts a planned position-time projection vectorat the planned position if the first aircraft is turned with thecalculated bank angle.
 2. The system of claim 1, further comprisingcoordinating the first aircraft with the at least one second aircraft inflight.
 3. The system of claim 2, further comprising computing an actualposition-time projection vector for the first aircraft and the at leastone second aircraft and guide the first aircraft and the at least onesecond aircraft to a rendezvous position.
 4. The system of claim 2,further comprising receiving a position of the at least one secondaircraft; and coordinating the planned position of the first aircraftwith the at least one second aircraft based on the position of the atleast one second aircraft.
 5. The system of claim 2, further comprisingcommanding the first aircraft to perform a banked turn with a secondbank angle if the planned position is missed by the at least one secondaircraft.
 6. The system of claim 1, further comprising communicating theperformance parameters between the first aircraft and the at least onesecond aircraft.
 7. The system of claim 1, wherein the first aircraft isa UAV and the at least one second aircraft is a UAV.
 8. The system ofclaim 1, further comprising calculating a current position of the firstaircraft.
 9. The system of claim 1, wherein the first aircraft is atanker aircraft and the at least one second aircraft is a receiveraircraft.
 10. The system of claim 1, further comprising displaying: theorbit pattern; the planned position and at least one planned velocityvector moving in real-time along the orbit pattern; the plannedposition-time projection vector; an actual position of the firstaircraft; and at least one actual position-time projection vector of thefirst aircraft based on at least one bank angle of the first aircraft,such that a user determines the planned position of the first aircrafton the planned position-time projection vector in order to arrive at apredetermined position at a correct time.
 11. A method for synchronizingaircraft positions in flight by action of an aerial refuelingsynchronization and rendezvous system, the method comprising:calculating by action of a processor a planned position on an orbitpattern of a first aircraft in flight and a planned position-timeprojection vector comprising at least one planned velocity vector of theplanned position-time projection vector; calculating a calculated bankangle by action of the processor such that the first aircraft interceptsthe planned position-time projection vector if the first aircraft turnswith the calculated bank angle; continuously and automatically receivingperformance information of a second aircraft for a duration of a syncevent and automatically adjusting the calculated bank angle based on theperformance information until synched; directing by action of theprocessor the first aircraft to turn early at the calculated bank anglefrom a current position to reach a future point ahead of the plannedposition on the planned position-time projection vector; and directingby action of the processor the first aircraft to intercept the plannedposition.
 12. The method of claim 11, further comprising directing thefirst aircraft to rendezvous with the second aircraft.
 13. The method ofclaim 11, further comprising calculating with the processor: the plannedposition-time projection vector of the first aircraft in timeincrements; effects of winds on the at least one planned velocity vectorof the planned position-time projection vector of the first aircraft;and an actual position-time projection vector in time increments of thefirst aircraft.
 14. The method of claim 13, further comprisingdisplaying on a display module: the planned position-time projectionvector of the first aircraft in time increments; the effects of thewinds on the at least one planned velocity vector of the plannedposition-time projection vector of the first aircraft; and the actualposition-time projection vector in time increments of the firstaircraft.
 15. A method of coordinating positioning of vehicles in motionby action of an aerial refueling synchronization and rendezvous system,the method comprising: calculating a current position of a first vehicleby action of a processor; calculating a planned position of the firstvehicle by action of the processor; calculating a calculated turn anglewith the processor such that the first vehicle intercepts a plannedposition-time projection vector when turned with the calculated turnangle; directing by action of the processor the first vehicle to turn atthe calculated turn angle from the current position to reach a futurepoint ahead of the planned position on the planned position-timeprojection vector; directing by action of the processor the firstvehicle to intercept the planned position on the planned position-timeprojection vector in anticipation of a sync event; synchronizing byaction of the processor the first vehicle with the planned position;continuously and automatically receiving performance information of asecond vehicle for a duration of the sync event and automaticallyadjusting the calculated turn angle based on the performance informationuntil synched to the planned position; and performing a rendezvousbetween the first vehicle and the second vehicle by action of theprocessor.
 16. The method of claim 15, wherein the step of performingthe rendezvous comprises: communicating performance parameters betweenthe first vehicle and the second vehicle; and determining a turn anglefor the first vehicle for turning ahead of the planned position to allowrendezvous with the second vehicle.
 17. The method of claim 16, whereinthe performance parameters comprise at least one member selected fromthe group consisting of: a first vehicle velocity, a first vehiclecoordinates, a second vehicle indication of contact with the firstvehicle, a second vehicle actual position, a second vehicle coordinates,a second vehicle velocity, a second vehicle waypoints, timinginformation, altitude, and a second vehicle waypoints desiredvelocities.
 18. The method of claim 15, further comprising calculatingwith the processor: the planned position-time projection vector of thefirst vehicle in time increments; effects of winds on a planned velocityvector of the planned position-time projection vector of the firstvehicle; and an actual position-time projection vector in timeincrements of the first vehicle.
 19. The method of claim 18, furthercomprising displaying on a display module: the planned position-timeprojection vector of the first vehicle in time increments; the effectsof the winds on the planned velocity vector of the planned position-timeprojection vector of the first vehicle; and the actual position-timeprojection vector in time increments of the first vehicle.
 20. Themethod of claim 15, further comprising directing the first vehicle toperform a banked turn with a second bank angle if the planned positionis missed by the second vehicle.